[Samba] [3.2.0] Off by one error

Jerry,

The 3.2.0 release is reporting this in the log.nmbd
[root@beta samba]# cat log.nmbd
[2008/07/02 12:26:52,* 0] nmbd/nmbd.c:main(849)
* nmbd version 3.2.0 started.
* Copyright Andrew Tridgell and the Samba Team 1992-2008
[2008/07/02 12:26:52,* 0] lib/util_str.c:safe_strcpy_fn(709)
ERROR: string overflow by 1 (16 - 15) in safe_strcpy [192.168.100.20/24]

Other than this issue; no real problems.
James

----
James Kosin


International Communications Group, Inc.
230 Pickett's Line
Newport News, VA* 23603

Phone: +1 (757) 947-1030 ext 122
Fax: +1 (757) 947-1035


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On Wed, Jul 02, 2008 at 12:32:46PM -0400, James Kosin wrote:[color=blue]
> Jerry,
>
> The 3.2.0 release is reporting this in the log.nmbd
> [root@beta samba]# cat log.nmbd
> [2008/07/02 12:26:52,* 0] nmbd/nmbd.c:main(849)
> * nmbd version 3.2.0 started.
> * Copyright Andrew Tridgell and the Samba Team 1992-2008
> [2008/07/02 12:26:52,* 0] lib/util_str.c:safe_strcpy_fn(709)
> ERROR: string overflow by 1 (16 - 15) in safe_strcpy [192.168.100.20/24]
>
> Other than this issue; no real problems.[/color]

Great (the no problems part) ! Can you attach with gdb to this error
message and get a backtrace when it occurs please ?

Thanks,

Jeremy.
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-----Original Message-----
From: Jeremy Allison [mailto:jra@samba.org]
Sent: Wednesday, July 02, 2008 12:57 PM
To: James Kosin
Cc: [email]samba@lists.samba.org[/email]
Subject: Re: [Samba] [3.2.0] Off by one error

On Wed, Jul 02, 2008 at 12:32:46PM -0400, James Kosin wrote:[color=blue]
> Jerry,
>
> The 3.2.0 release is reporting this in the log.nmbd
> [root@beta samba]# cat log.nmbd
> [2008/07/02 12:26:52,* 0] nmbd/nmbd.c:main(849)
> * nmbd version 3.2.0 started.
> * Copyright Andrew Tridgell and the Samba Team 1992-2008
> [2008/07/02 12:26:52,* 0] lib/util_str.c:safe_strcpy_fn(709)
> ERROR: string overflow by 1 (16 - 15) in safe_strcpy [192.168.100.20/24]
>
> Other than this issue; no real problems.[/color]

Great (the no problems part) ! Can you attach with gdb to this error
message and get a backtrace when it occurs please ?

Thanks,

Jeremy.

---
Jeremy,

I'd need some pointers, I'm not all that familiar with gdb, and there is no way to stop on the error. NMDB still runs after displaying this; so, I don't think a back-trace will help find it when I kill the process.

It looks as though it may be trying to copy the allowable IP addresses into a structure that only has space for 15 characters. The ip [192.168.100.20/24] ends up being in the config file
[root@beta samba]# cat smb.conf | grep 192.168.100.20/24
interfaces = 192.168.100.20/24



James

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On Wed, Jul 02, 2008 at 02:09:48PM -0400, James Kosin wrote:[color=blue]
> -----Original Message-----
> From: Jeremy Allison [mailto:jra@samba.org]
> Sent: Wednesday, July 02, 2008 12:57 PM
> To: James Kosin
> Cc: [email]samba@lists.samba.org[/email]
> Subject: Re: [Samba] [3.2.0] Off by one error
>
> On Wed, Jul 02, 2008 at 12:32:46PM -0400, James Kosin wrote:[color=green]
> > Jerry,
> >
> > The 3.2.0 release is reporting this in the log.nmbd
> > [root@beta samba]# cat log.nmbd
> > [2008/07/02 12:26:52,* 0] nmbd/nmbd.c:main(849)
> > * nmbd version 3.2.0 started.
> > * Copyright Andrew Tridgell and the Samba Team 1992-2008
> > [2008/07/02 12:26:52,* 0] lib/util_str.c:safe_strcpy_fn(709)
> > ERROR: string overflow by 1 (16 - 15) in safe_strcpy [192.168.100.20/24]
> >
> > Other than this issue; no real problems.[/color]
>
> Great (the no problems part) ! Can you attach with gdb to this error
> message and get a backtrace when it occurs please ?
>
> Thanks,
>
> Jeremy.
>
> ---
> Jeremy,
>
> I'd need some pointers, I'm not all that familiar with gdb, and there is no way to stop on the error. NMDB still runs after displaying this; so, I don't think a back-trace will help find it when I kill the process.[/color]

What you can do is attach to the running process with :

gdb /usr/local/samba/sbin/nmbd
b lib/util_str.c:safe_strcpy_fn:709
attach <pid>
continue

Then when the breakpoint triggers you can type :

bt

to get the backtrace, and also go up the stack
and type out the local variables.

If it happens every time you start nmbd then
that's easier, just type :

gdb --args /usr/local/samba/sbin/nmbd -i
b lib/util_str.c:safe_strcpy_fn:709
run

Thanks !

Jeremy
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----- Original Message -----
From: "Jeremy Allison" <jra@samba.org>
Newsgroups: linux.samba
Sent: Wednesday, July 02, 2008 2:20 PM
Subject: Re: [Samba] [3.2.0] Off by one error

[color=blue]
>[color=green]
>> I'd need some pointers, I'm not all that familiar with gdb, and there is
>> no way to stop on the error. NMDB still runs after displaying this; so,
>> I don't think a back-trace will help find it when I kill the process.[/color]
>
> What you can do is attach to the running process with :
>
> gdb /usr/local/samba/sbin/nmbd
> b lib/util_str.c:safe_strcpy_fn:709
> attach <pid>
> continue
>
> Then when the breakpoint triggers you can type :
>
> bt
>
> to get the backtrace, and also go up the stack
> and type out the local variables.
>
> If it happens every time you start nmbd then
> that's easier, just type :
>
> gdb --args /usr/local/samba/sbin/nmbd -i
> b lib/util_str.c:safe_strcpy_fn:709
> run
>
> Thanks !
>
> Jeremy[/color]

I'll have to get back to you later on the backtrace gdb is broken on my
machine.
It is 100% reproducable by including an interfaces line with the IP and mask
as the parameter. And only happens on startup when nmbd is loading the
configuration. If I change the interfaces line to read just the single IP
without the mask all is fine.
I'll check to see if this was a change to how the interface line is
specified or a problem that has always been there. And wasn't caught until
safe-copy was used.

interfaces 192.168.100.20/24
breaks the nmdb with an error; but doesn't stop nmdb.
interfaces 192.168.100.20
works and no error is reported.

James Kosin

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On Wed, Jul 02, 2008 at 06:46:50PM -0400, James Kosin wrote:
[color=blue]
> I'll have to get back to you later on the backtrace gdb is broken on my
> machine.
> It is 100% reproducable by including an interfaces line with the IP and
> mask as the parameter. And only happens on startup when nmbd is loading
> the configuration. If I change the interfaces line to read just the single
> IP without the mask all is fine.
> I'll check to see if this was a change to how the interface line is
> specified or a problem that has always been there. And wasn't caught until
> safe-copy was used.
>
> interfaces 192.168.100.20/24
> breaks the nmdb with an error; but doesn't stop nmdb.
> interfaces 192.168.100.20
> works and no error is reported.[/color]

Ok, I've found it. It's a warning, not an error.
We've correctly set up the interface here but
we're just trying to set the interface name.

It happens here lib/interface.c:

472 safe_strcpy(ifs.name, token, sizeof(ifs.name)-1);

Where token is set to "192.168.100.20/24" which is greater
than ifs.name. We've already parsed out the values for
ss, ss_mask and ss_bcast we're just trying to give the
pseudo interface a name.

I'll replace this with strlcpy and it should be fine.

Thanks for the report though !

Jeremy.
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